Apparatus for uniformly inductively heating crankshafts

ABSTRACT

When inductively heating crankshaft workpieces, there is a tendency for the crank webs to become locally overheated during heating of crankpin portions of the rotating crankshaft workpieces. This is overcome by the invention by the provision of two cooling arms which are located one on each side of the inductor and pivoted in the manner of a pendulum to swing parallel thereto, and which are biassed for motion towards the crankshaft during rotation of the crankshaft, whereby the portion of the crankshaft liable to overheating is effectively cooled during the portion of revolution of the workpiece.

United States Patent HEATING CRANKSHAFIS 7 Claims, N0 Drawings US. Cl 266/4, 148/146, 219/1043, 219/1057 Int. Cl C2ld 1/66 Field of Search 266/6, 65,

Primary Examiner-Andrew R. Juhasz Assistant Examiner-James F. Coan Att0rney-Cushman, Darby & Cushman ABSTRACT: When inductively heating crankshaft workpieces, there is a tendency for the crank webs to become 10- cally overheated during heating of crankpin portions of the rotating crankshaft workpieces. This is overcome by the invention by the provision of two cooling arms which are located one on each side of the inductor and pivoted in the manner of a pendulum to swing parallel thereto, and which are biassed for motion towards the crankshaft during rotation of the crankshaft, whereby the portion of the crankshaft liable to overheating is effectively cooled during the portion of revolution ofthe workpiece.

APPARATUS FOR UNIFORMIJY INDUCTIV ELY HEATING CRANIfSI'IAFIS This invention relates to the inductive hardening of the crankpins of crankshafts for internal combustion engines and particularly relates to apparatus for use in the so-called rotary method, in which an inductor forming a closed heating conductor loop on one side of the crankpin is yieldingly in contact with the surface thereof, and electrical power is then applied at a constant rate to the inductor whilst the crankshaft is rotated at constant speed about the axis of symmetry of the mainshaft bearing or of the crankpin.

Provided that only the bearing surface of the crankpin is required to be inductively heated and hardened by subsequent quenching, difficulties do not usually arise.- However when the fillets and the adjoining retaining surfaces of the websas well as the bearing surfaces are to be hardened, the maintenance of a constant speed of rotation and of a constant supply of electrical power does not result in the production of a uniformly heated layer in the surfaces to be hardened unless precautions are taken. This is due to the fact that the crankpins of 1 crankshafts are situate between crank webs offset a considerable distance from the axis of symmetry of the crankshaft, the crank webs often having a large mass.lf electrical power is induced in the crankpins at a constant rate the heat generated in the workpiece flows along the surface of the crankpin facing the axis of symmetry of the crankshaft, ie the inside-facing surface, into the webs of the cranks. Moreover heat flow is considerably impeded in the small remaining portions of the webs which surround the outside surfaces of the crankpins.

If therefore the power supplied is based on the requirements of the inside-facing surfaces of the crankpins, considerable local overheating occurs and stress cracks may result after hardening. If however the supply of electrical power is based on the requirements of the outside-facing surfaces of the crankpins.i.e. surfaces facing away from the axis of symmetry of the crankshaft, this may lead to the inside-facing surfaces thereof being insufficiently hardened.

In order to achieve a satisfactory inductive hardening effect according to the'invention the supply of electric heating energy is based on the heat requirements of the inside surface of the crankpin workpiece and to avoid overheating the fillet portion and retaining faces of the webs on the outside of the workpiece cooling is effected, which may .be effected by conventional cooling techniques. Y

While cooling of the crankwebs should be effective, it must also be achieved by the simplest possible mechanical means, and it is therefore the object of the invention to provide a solution of this problem-by the provision of controlled moveable cooling means.

The invention provides in inductive heating apparatus for inductively heating the bearing surfaces of a crankshaft workpiece, of the type comprising means for rotatinga crankshaft workpiece along a longitudinal axis thereof and an inductor for inductively heating the overall surface thereof: cooling means for the said crankshaft comprising t \o pendulum cooling arms, one of which is located on each side'of the inductor and suspended so as to swing parallel to the said inductor, and control means for positively controlling the movement of the said pendulum cooling arms in response to rotation of the crank webs of the crankshaft workpiece.

The required pressure for maintaining contact can be readily provided in conventional manner by springs, hydraulic or pneumatic means or by the provision of simple lever linkages.

However, in a particularly simple and advantageous embodiment of the invention the pendulum arm may be maintained in contact with the crank webs by gravity. In' the direction towards the bearing surface and the swinging motion of the pendulum arm is limited by a stop. The pendulum cooling arms may consist of a plurality of tube elements adapted to conduct cooling fluid, of which one is provided with nozzle orifices.

According to another feature of the invention a cooling fluid flows through the pendulum cooling arm at a rate which depends upon the angular position ofthat arm. To this end the two pendulum arms may communicate through a tube common to both, which contains an opening and which is rotatably mounted in the inductor, said tube beingtinserted into a sealed guide member provided with a connection for the supply of a liquid cooling fluid.

Alternatively, each pendulum arm may be connected to a separate tube rotatably mounted in the inductor, each tube being provided with an opening in the region of a connection for the supply of a liquid cooling fluid in a sealed guide member in which the tube is inserted.

This form of construction in which the cooling pendulum arms on each side of the inductor are' not rigidly interconnected is to be preferred when the webs adjoining the crank-- pin that is to be hardened are of different configurations.

An embodiment of the invention is'hereinafter described and illustrated in the accompanying drawings.of which:

FIG. 1 and FIG. 2 are cross-sectional representations showing the position of the pendulum cooling arms in two extreme positions of the crank webs of a crankshaft rotating about its mainshaft bearings,

FIG. 3 is a perspective part sectional view of the suspension of the pendulum cooling arms, and

FIG. 4 and FIG. 5 illustrate the disposition of the connection for the supply of a cooling liquid and of the connecting pipe for the embodiment according to FIG. 1 and FIG. 2.

Referring to FIG. 1, an inductor I which is yieldingly applied to the bearing surface of a crankpin 3 with the interposition of spacing elements 2. The crankshaft rotates about the axis of symmetry of the mainshaft bearing in the direction indicated by the arrow 4. The contours of the crank webs are indicated in discontinuous lines 5.

A pendulum cooling arm 6 maintains contact with the crank webs 5 and is pendantly deflected about a pivot 7 by the revolving crank webs. In order to increase the pull of gravity the pendulum arm 6 is provided with a weight 8. A transverse portion of the said arm 6 has a plurality of orifices 9. In the position shown in FIG. 1 the supply of cooling fluid as hereinafter described, is cut off. In this position the crank webs need not be cooled since the inside surface of the crankpin is being inductively heated.

In FIG. 2 the crankwebs have rotatedfrom their position in FIG. 1 through an angle of The outside surface of the crankpin 3 is now within the range of action of the inductor. In order to prevent the ends of the crank webs on each side of the outer surface of the crankpin from being overheated, a cooling liquid is sprayed from the nozzle orifices 9 on the parts of the workpiece that are liable to overheat. The pendulum arms 6 have of their own accord moved into the position according to FIG. 2. The swing of the arms 6 towards the bearing surface is limited by stops l0.

FIG. 3 illustrates the suspension of the pendulum cooling arms and the manner in which the rate of coolant supply is controlled. Communication between two pendulum arms (not shown) which are located outside the side plates 11 of the inductor is provided by a tube 12 which has an opening The The tube 12 is inserted between the side plates 11 in a guide member 15 provided with seals 14 and with a connection 16 for the supply of a coolant. The tube 12 oscillates in the guide member as the pendulum cooling arms'6 swing to and fro. Hence the opening 13 will at certain times register exactly with the opening ofthe connection 16 for the coolant and at other times it will not be in communication therewith, thereby cutting off the flow of the coolant.

The relative positions of the two openings are shown in FIG. 4 and FIG. 5 when the pendulum cooling arms are in the positions according to FIG. I and FIG. 2. As shown in FIG. 4 the opening 13 is provided in the tube 12in a position in which it is completely cut off from the connection 16 for the coolant supply when the pendulum arms are in the position illustrated in FIG. I. The cooling liquid therefore remains stationary in the supply pipe and cannot enter the pendulum arms.

However, when the pendulum arms have swung into the position according to FIG. 2, the tube 12, as shown in FIG. 5, will have been turned so that its opening 13 is in register with the connection 16 for the coolant supply. The cooling liquid can therefore now flow into the pendulum arms whence it issues from the nozzle orifices 9 to cool the cooperating parts of the workpiece as desired.

lclaim:

1. In inductive heating apparatus for inductively heating the bearing surfaces of a crankshaft workpiece, of the type comprising means for rotating :1 crankshaft workpiece along a longitudinal axis thereof and an inductor for inductively heating the overall surface thereof: cooling means for the said crankshaft comprising two pendulum cooling arms, one of which is located on each side of the inductor and suspended so as to swing parallel to the said inductor, and control means for positively controlling the movement of the said pendulum cooling arms in response to rotation of the crankwebs of the crankshaft workpiece.

2. Apparatus according to claim 1, in which the pendulum arms are maintained in contact with the crank webs by gravity.

3. Apparatus according to claim 1, in which the motion of the pendulum arms towards the bearing surface of a workpiece being inductively heated,-is limited. 7 I

4. Apparatus according tolclaim 1', in which cooling fluid flows through the pendulum arms at a rate controlled by the angular position of the said pendulum v 5. Apparatus according to claim 4, in which.the pendulum arms comprise a pluralityof tube elements, adapted to conduct cooling fluid, of which one-tube-element is provided with nozzle orifices. r

6. Apparatus according to claim; 11-, inwhich both pendulum arms are in communication with acommon tube rotatably mounted in the inductor in a sealedguide member, the said tube being provided with an openingdisposed to cooperate with a tube connection for the supply of cooling liquid therethrough. r

7. Apparatus according to claim 1, in which each pendulum arm is in communication with a tube rotatably mounted in the inductor in a sealed guide member, the said tube being provided with an opening disposed to cooperate with a tube connection for the supply of cooling liquid therethrough, 

1. In inductive heating apparatus for inductively heating the bearing surfaces of a crankshaft workpiece, of the type comprising means for rotating a crankshaft workpiece along a longitudinal axis thereof and an inductor for inductively heating the overall surface thereof: cooling means for the said crankshaft comprising two pendulum cooling arms, one of which is located on each side of the inductor and suspended so as to swing parallel to the said inductor, and control means for positively controlling the movement of the said pendulum cooling arms in response to rotation of the crankwebs of the crankshaft workpiece.
 2. Apparatus according to claim 1, in which the pendulum arms are maintained in contact with the crank webs by gravity.
 3. Apparatus according to claim 1, in which the motion of the pendulum arms towards the bearing surface of a workpiece being inductively heated, is limited.
 4. Apparatus according to claim 1, in which cooling fluid flows through the pendulum arms at a rate controlled by the angular position of the said pendulum arms.
 5. Apparatus according to claim 4, in which the pendulum arms comprise a plurality of tube elements adapted to conduct cooling fluid, of which one tube element is provided with nozzle orifices.
 6. Apparatus according to claim 1, in which both pendulum arms are in communication with a common tube rotatably mounted in the inductor in a sealed guide member, the said tube being provided with an opening disposed to cooperate with a tube connection for the supply of cooling liquid therethrough.
 7. Apparatus according to claim 1, in which each pendulum arm is in communication with a tube rotatably mounted in the inductor in a sealed guide member, the said tube being provided with an opening disposed to cooperate with a tube connection for the supply of cooling liquid therethrough. 